Surfactants are amphiphilic compounds comprising a polar or ionic head group and a hydrophobic tail. Anionic surfactants have important commercial applications as wetting agents and detergents. For example, current methods for removing petroleum from underground reserves typically leave a substantial amount of unrecoverable residual oil. One approach to the recovery of this residual petroleum is surfactant-based enhanced oil recovery. In this method, an aqueous surfactant solution is injected into an oil well at a late stage of depletion to extract the residual oil. Development of such enhanced oil recovery methods was an area of active research in the petroleum industry in the 1970s and 1980s and resulted in several pilot field processes.
Surfactants typically used in enhanced oil recovery processes have sulfonate or sulfate polar head groups due to the aqueous solubility of such compounds in the presence of hard cations often present in such environments, such as Mg.sup.2+ and Ca.sup.2+. Such surfactants include alkylsulfonates, alkylarylsulfonates and petroleum sulfonates. More recently, the development of surfactant-based enhanced oil recovery methods has declined dramatically, due, in part, to high surfactant costs. As a result, the development of low-cost surfactants derived from waste products, such as lignin, is an active area of research in the petroleum industry.
There is, thus, a need for a surfactant suitable for use in an enhanced oil recovery process which is derived from inexpensive starting materials.